1. Field of the Invention
The present invention generally relates to devices for monitoring and detecting entry to a shipping container. The invention more particularly relates to devices and methods that sense, analyze, and interpret movement of a nearby object to detecting motion of a movable portion of the latch mechanism of a shipping container.
2. Description of the Prior Art
In the shipment of goods throughout the world, the use of standardized containers to house the goods during shipment and storage has become widespread. Standardized containers provide ease of handling and adequate security of large volumes of goods as they pass through the intermodal transport networks and systems, and international ports all over the globe. A variety of systems, methods, and devices have been developed for tracking and monitoring the containers en route and in storage, as well as managing the routing and handling of containers during loading, unloading, inspection, shipment, storage, delivery, etc. Other systems, methods, and devices are in use for ensuring security of the containers and their contents. These include various kinds of locks, sealing mechanisms, signaling devices, alarms, monitoring units, etc., designed to detect tampering with a shipping container or its door and provide an indication of a tampering event therewith.
Standardized shipping containers are rectangular boxes constructed to be joined with a standardized truck chassis, or placed or stacked on a railcar chassis or shipboard space for shipping from one place (origin) to another (destination). The containers may be manipulated and stacked in a shipping yard for storage, or handling according to routing data for dispatch to a destination. The containers are typically equipped with standardized doors at one end. Typically there are two doors, hinged along the outside vertical edge of the door opening, each door extending the full height of the door opening of the container, and each extending laterally for half the width of the container. The doors each employ a standardized latch mechanism having at least one vertical rod or pole that, when rotated through an angle by a hand lever attached to the rod, moves a latching arm fixed to each end of the rod into a latched position with a receptacle on the container at the edge of the door opening just above and below the door opening. Most such shipping containers have two such latching mechanisms on each door. Thus, four such rotating rod latching mechanisms may be spaced at approximately uniform intervals across the width of the container.
As described herein below, a number of solutions have been disclosed to provide some sort of sealing device attached to the door or to its latch that must be broken or damaged to gain access to the container. Some sealing devices provide an indication that the device was subject to tampering at some time previous to a first notice of the condition of the device. Other devices, such as a switch or other sensing mechanism placed in a bridging relationship with the door and the container, may provide a signal or alarm from the switch or sensing mechanism when the door of the container is moved away from the container opening.
U.S. Pat. No. 4,750,197 issued to Denekamp et al. discloses a security system for containers that includes door sensors having magnets embedded inside each door and Hall Effect sensors positioned on the container to sense the magnetic field of the magnets when the doors are closed. Signals from the sensors may be coupled to a monitoring unit, along with outputs of other sensors in the container that are responsive to certain conditions.
U.S. Pat. No. 4,841,283 issued to Bubliewicz discloses a two-part hinge having a rotation detector embedded in a knuckle portion of the hinge, one part a stationary portion having a spaced-apart emitter and detector, the other a rotating shield plate that rotates into or out of the space between the emitter and detector as the hinge leaves are swung about the hinge pivot.
U.S. Pat. No. 6,069,563 issued to Kadner et al. discloses an electronic seal having a conductive loop that forms part of a circuit for detecting resistance changes in the loop as an indication of tampering with the loop. The loop may be enclosed in a pin or otherwise coupled into a seal body containing detection and signaling circuitry. A detection event may be stored or transmitted, and the circuitry may operate in sleep and active modes.
U.S. Pat. No. 6,265,973 issued to Brammall et al. discloses an electronic seal configured as a conductive bolt and a cavity having electrical contacts in a locking body for receiving the bolt. The locking body attaches to a container door. The bolt secures hasps of the container door latch to the locking body, and completes a circuit within the locking body. If the bolt is severed or removed, the circuit responds by transmitting a signal to a local reader.
U.S. Pat. No. 6,281,793 issued to Haimovich et al. discloses an electronic seal body for receiving both ends of a seal wire and connecting them to a circuit that senses a change in an electronic parameter, such as a resistance change as described in U.S. Pat. No. 6,002,343, that is unreadable except upon disengagement of the seal wire from the seal body. The seal body is attached to the object being protected. The seal wire may be passed through a movable part of the object being protected.
U.S. Pat. No. 6,400,266 issued to Brown, Jr. discloses a trailer having a door, a locking mechanism for securing the door, and a sensor for sensing a closed and secured door. The sensor, mounted on a stationary part of the trailer, may be a proximity, mechanical, Hall Effect, photo eye, or laser sensor. The sensor may detect the presence or the absence of a ferrous or opaque object in the locking mechanism. Sensor output signals may be used for various control functions.
U.S. Pat. No. 6,747,558 issued to Thorne et al. discloses a seal tag for a container including a locking device, which includes a bolt that passes through holes in the arms of a U-shaped member. The bolt also passes through the center of first and second coils disposed around the holes in the ends of the arms and the closed ends of a hasp assembly attached to the container and positioned between the arms. Tampering with the bolt affects the magnetic field respectively established and monitored by the coils, enabling detection of the tampering. The detection signal may be transmitted or accessed externally.
U.S. Pat. No. 6,870,478 issued to Cockburn et al. discloses a monitoring unit for attachment to a secured item such as a container locking rod. A switch in a mounting bracket of the monitoring unit arms its alarm circuit when attached and causes an alarm if the mounting bracket is removed.
U.S. Pat. No. 7,242,296 issued to Wang et al. discloses a door closure monitor installed on the inside of one door of a container and a door displacement transducer mounted in juxtaposition on the opposite door of the container. The displacement transducer may be a proximity switch, a pressure transducer, or a position switch. The transducer enters one state or the opposite state depending on the spatial relationship of the transducer and the closure monitor. An electronic circuit communicates the state of the monitor via an antenna.
U.S. Patent Application Publication No. 2006/0103524 filed by Auerbach et al. discloses an electronic seal for a shipping container lock similar to the seal of the Kadner patent (U.S. Pat. No. 6,069,563). An electronic seal wire enclosed in a frangible hollow shaft is configured for press-fit engagement with a socket. Breaking the shaft or removing the pin from the socket breaks the seal. One reusable embodiment includes a reed switch in the shaft operated by a magnet in the socket portion.
U.S. Patent Application Publication No. 2007/0285240 filed by Carroll et al. discloses a high-resistance cable coupled to a microprocessor that detects resistance changes as an electronic seal and stores the time of the change in memory. An active RFID transceiver communicates the status on demand of a remote reader.
U.S. Patent Application Publication No. 2007/0285240 filed by Sensenig et al. discloses preferred use of passive RFID devices on shipping containers for monitoring by active devices on the vehicle carrying the container or other locations close to the container's position. The active devices include GPS and processing apparatus for monitoring and tracking ID and location data.
A common characteristic of the foregoing devices and methods is that they employ a digital or binary approach by determining which of two states exists. For example, whether a door is open or closed, or a seal is broken or intact. Thus, in such systems, tampering is detected as an either/or event, without the ability to reject false indications that may appear to be tampering but actually are not tampering. A further difficulty with the either/or approach is that a “positive” indication by the prior art devices is no more informative or reliable than a likelihood of tampering. Similarly, in some of the devices, an attempted tampering event may not be detected or may be in process but goes undetected until a gross change has occurred in the sensing apparatus being monitored. Other devices and methods store the detection information for retrieval some time after the detection event actually occurred. Such indications are weaknesses in the security of shipping containers and their contents, particularly in an environment where loss prevention and terrorism interdiction are important objectives.
What is needed is an intelligent system, method, and apparatus that can detect, analyze, and distinguish a variety of potential container breach events, and make the detection information available in real time, so that accurate and timely information about attempted or realized breach of a container can be developed and made available to shipping authorities.